Control system for clothes dryers



June 1, 1965 RALEY 3 1 86,107

CONTROL SYSTEM FOR CLOTHES DRYERS Filed June 25, 1962 F'IG.\

I 3 Sheets-Sheet 1 INVENTOR. HOWARD F. RALEY BYMWW H \S ATTORNEV 5 Sheets-Sheet 2 alllillllllllllllllllllll n- H. F. RALEY CONTROL SYSTEM FOR CLOTHES DRYERS June 1, 1965 Filed June 25, 1962 June 1, 1965 H. F. RALEY 3,185,107

CONTROL SYSTEM FOR CLOTHES DRYERS Filed June 25, 1962 3 Sheets-Sheet 3 FIGB INVENTOR. HOWARD F. RALEY WWW H\S ATTORNEY United States Patent Oflice Patented June 1, 1965 3,186,107 C(BNTROL SYSTEM FOR CLQTHES DRYERS Howard F. Raley, Louisville, Ky, assignor to General Electric Company, a corporation of New York Filed June 25, 1962, Ser. No. 2194,94!) 4 Claims. (CI. 34-45) This invention relates to clothes drying machines, and more particularly to automatic control systems for controlling the drying operation in such machines.

There are .at the present time several domestic clothes drying machines commercially available where the length of the heating cycle is controlled by the dryness of the clothes. This is generally effected by using a thermostatic control, on the basis that a predetermined rise in the clothes temperature indicates that the heat energy applied to the clothes is no longer being .used to vaporize moisture from them but, instead, is free to raise the temperature. In other words, such control systems utilize a predetermined high temperature as a trip point for shutting off the means provided for heating the clothes.

Depending upon the type of fabric being dried, and the size of the load, either a single such occurrence may be suflicient or several such heating cycles may be required in a single drying sequence. The number of heating cycles is usually determined by having .a timer run each time the heater shuts .ofl, with the total length of timer operation being preselected; when the-full period of timer operation has tolled, the machine is shut off.

Where several such cycles are required, it is desirable to provide a corrective action to compensate for the effect of ditfcrerences in the temperature of ambient air on the operation of the clothes dryer. In this connection, when low temperature ambient air is being brought in, the dryer runs for a substantially longer time before the predetermined high temperature trip point is reached, and therefore a greater amount of drying is performed than where ambient air is brought in at a higher temperature and consequently less time is required for the trip temperature to be reached.

To compensate for this, I propose to cause variation in the amount of time that the timer runs between heater operations; for instance, where low temperature ambient air is provided, and there is therefore a longer operation of the heater each time before the trip point is reached, a longer period of timer operation should be provided after each trip so .as to decrease the total number of heater cycles. In other words, selection of a certain length of timer operation will cause a smaller number of heater cycles Where the ambient temperature is low than where the ambient temperature is high.

It is therefore .an object of my invention to provide, in a dryer having a thermostatic control of the general type described, improved .and economical means of compensating for ambient temperature changes.

A further more specific object of my invention is to achieve such compensation by increasing the length of time that the timer operates between the heater operations as the ambient temperature decreases.

In carrying out my invention in one form thereof, I provide a clothes dryer in which a clothes receiving chamber is connected by an inlet duct and'an exhaust duct to the ambient air, with suitable means being provided for moving air through the inlet duct means to the chamber and then out through the exhaust duct. Upstream of the chamber, there is .a heater so that the air is heated before passing into the chamber, and the machine is provided with a timer which is presettable for varying lengths of time. A control thermostat, positioned to be responsive to clothes temperature, has a first position at relatively low temperature in which it completes a heater energizing circuit; the thermostat moves to a second position at a predetermined higher temperature to open the heater circuit and enable completion of a circuit for energizing the timer. Upon cooling, the thermostat r e-establishes the heater circuit and opens the timer circuit. After the timer runs for the pro-selected period, it de-energizes both circuits to terminate operation of the dryer.

The length of time that the timer operates after each trip of the control thermostat from its first position to its second position is controlled by a b-imetal means which is positioned to sense the ambient temperature and also is arranged to be heated in response to energization of the timer circuit. The bimetal means is in controlling relation to the timer circuit, so that when it reaches a predetermined temperature it causes the timer circuit to be opened. Since the bimetal means is sensitive to ambient temperature, the colder the ambient air the longer the heating thereof needs to be carried out in order to reach the predetermined temperature where it opens the timer circuit.

The subject matter which I regard as my invent-ion is particularly pointed out and distinctly claimed in the concluding portion of this specification. My invention, however, both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.

In the drawings, FIGURE 1 is a side elevati-onal view of a clothes dryer incorporating my improved dryer control arrangement, the view being partly broken away and partly sectionalized to illustrate details;

FIGURE 2 is a horizontal sectional view of the dryer, with certain surfaces broken away and partly sectionalized to illustrate further details; and

FIGURE 3 is a schematic illustration of my improved control circuit.

Referring now to FIGURES 1 and 2 'of the drawings, I have shown therein a domestic clothes dryer 1 including a clothes tumbling container or drum 2 provided within a suitable outer casing or cabinet 3 which completely encloses it on all sides. The drum is mounted for rotation within cabinet 3 on a substantially horizontal axis, and is generally cylindrical in shape, having a first outer wall portion 4, second and third outer wall portions 5 and 6 located respectively adjacent the ends of the drum, a back wall 7, and a front wall 8. Outer wall portions 4, 5 and 6 are imperforate over their entire length so that the entire out-er shell of the basket is imperforate; on the interior surface of central portion 4 there is provided a plurality of clothes tumbling ribs 9.

The front of drum 2 is rotatably supported within the outer casing 3 by means of a pair of idler roller Wheels 10 and 11 (FIGURE 2) which are rotatably secured to the top of an upwardly extending member 12 secured at its bottom to the base 12a of the machine (FIGURE 1). It will be observed that rollers 10 and 11 are disposed beneath the drum in contact with portion 6 thereof. The rear end of the drum receives its support from roller wheel 13 which is positioned beneath portion 5 of the drum in supporting and frictionally driving engagement therewith.

Roller 13 is mounted on a shaft 14 supported in bearings 15. Shaft 14 is secured to a pulley 16 which is driven from a belt 17 in turn powered by a pulley 18 mounted on the end of a shaft 19 of an electric motor 20. The motor, pulleys, and roller 13 are so proportioned to drum 2 and to each other that drum 2 is rotated by roller 13 at an appropriate speed to provide tumbling action for articles of clothing placed therein.

In order that a stream of drying air may be introduced into and passed through the clothes drum, the drum is provided with a central aperture 21 in its front wall 8 and with a plurality of perforations 22 extending in an annulus around back wall '7. Rigidly secured to the rear wall 23 of casing 3 by any desired means such as, for instance, welding at suitable points 24, is a baffle member 25 which has secured thereto heating means 26 appropriately insulated from the baffle member. Heating elements 26 may be annular in shape so as to be generally coextensive with the perforations 22 in drum 2. A baffle member 27 is rigidly secured to the back wall 7 of the drum outside the ring of perforations 22 and within the stationary bafile 25 so that an annular air inlet 28 is in effect formed by the two b'afiles 25 and 27. Battle 27 is further provided with an annular series of openings 29; in this manner a passage is created for air to enter annular opening 28 between the baffles, pass over the heating elements 26, through openings 29 and then through perforations 22 into the interior of drum member 2.

In addition to the air guiding function, the baffles 25 and 27 help the rollers 10, 11 and 13 support the drum 2. Secured to the central portion 30 of baffle 27 is a bracket 31 to which in turn is secured a stub shaft member 32 arranged substantially coaxially with drum 2. The central portion of baffle 25 has an opening 34 formed therein in the shape of a slot. This slot is suitably formed (as more fully described in Patent 3,009,259, issued on November 21, 1961, to William F. Simpson, and assigned to General Electric Company, assignee of the present invention) so as to permit stub shaft 32 a limited amount of movement in the vertical direction but virtually no movement in a horizontal direction. Thus, the slight vertical motions of the drum which result from the tumbling of the clothes can be accommodated while at the same time undesirable horizontal motion is affirmatively prevented by the engagement of stub shaft 32 in slot 34.

The front opening 21 of the drum is substantially closed by means of a stationary bulkhead generally indicated by the numeral 35. Bulkhead 35 is made up of a number of adjacent members including the inner surface 36 of an access door 37 mounted on the dryer cabinet, a stationary frame 38 for the door, the inner surface 39 of an exhaust duct 40, and an annular flange 41 mounted on the frame 38 and on the duct wall. It will be noted that a suitable clearance is provided between the inner edge of the drum opening 21 and the edge of bulkhead 35 so that there is no rubbing between the drum and the bulkhead during rotation of the drum. In order to prevent any substantial air leakage through opening 21 between the interior and the exterior of the drum, a suitable ring seal 42 preferably formed of felt-like material is secured to flange 41 in sealing relationship with the exterior surface of drum Wall 8.

Front opening 21, in addition to serving as part of the air flow path through the drum, also serves as a means whereby clothes may be loaded into and unloaded from the drum. The door 37 whose inner surface forms part of the bulkhead closing the opening is mounted on cabinet 3, and when the door is opened clothes may be inserted into or removed from the drum through the door frame 38. It will be noted that the door includes an outer fiat imperforate section 43 and an inwardly extending hollow section 44 mounted on the fiat outer section. Hollow section 44 extends into the door frame 38 when the door is closed, and the door surface 36 which comprises part of the combination bulkhead 35 is actually the inner wall of this hollow section.

The air outlet from the basket is provided by a perforated opening 45 formed in the inner wall 36 of hollow door section 44. The bottom wall section of door 44 and the adjacent wall of door frame 38 are provided with aligned openings 46 and 47, opening 47 providing the entrance to duct 40. As shown, a lint trap 48, which may comprise a fine mesh bag, is preferably positioned in exhaust duct 40 at opening 47, the bag being supported by the door frame 38.

Duct 40 leads to suitable air moving means which may, as shown, comprise a centrifugal blower 49 mounted on the motor shaft and thus driven by motor 20. The outlet of blower 49 communicates with an outlet duct 50 (FIG URE 2) which extends to an opening 51 in the back 23 of cabinet 3. During operation of motor 20 the rotation of blower 49 causes air to be drawn into cabinet 3 from atmosphere through a suitable opening 51a, through annular opening 28, over heaters 26, through openings 29 and perforations 22 into drum 2, across the drum, through perforated opening 45 and aligned openings 46 and 47 into duct 40, and through the blower 49, the outlet duct 50, and opening 51 to atmosphere.

The operation of dryer 1 is controlled by my new and improved system as shown in FIGURE 3. The entire control system of the machine is energized across a threewire power supply system, including supply conductors 52 and 53 and a neutral conductor 54. For domestic use, the conductors 52 and 53 will normally be connected across a 220 volt power supply, with 110 volts appearing between the neutral line 54 and each of these conductors.

The drive motor 20 includes a main winding 55 and a start winding 56 which are connected in parallel with each other between supply conductor 52 and neutral conductor 54. Specifically, the circuit, starting at neutral conductor 54, passes first through a conventional door switch 57 of the type which is closed when door 37 is closed and is open when the door is opened. The circuit then extends through a conductor 58, which may include a conventional motor protector 59, to the windings 55 and 56 in parallel with each other. Winding 55 is directly connected to a conductor 60, While winding 56 i connected to conductor 60 through a centrifugal switch member 61 which is shown in its position of rest.

Conductor 60 includes a push button switch 62 which is biased to an open position, .and terminates in a cont-act 63 engageable by a switch arm 64 connected to supply conductor 52. It will be understood that switch arm 64 is conventionally controlled by a cam follower 65 which in turn is under the guidance of a cam 66 secured to be rotated by a timer 67. When the cam 66 is in the position shown, contact arm 64 and contact 63 are disengaged; upon rotation of the cam from that position by suitable manual means 68 the cam follower will rise, carrying switch arm to 64 with it so as to cause the switch arm to engage contact 63. Manually operable means 68, schematically shown in FIGURE 3, is conventionally carried on a backsplasher panel 69 as shown in FIGURE 1.

Switch arm 61 is under the control of a centrifugal member, schematically shown by the numeral 70, secured to rotate with the rotor 71 of motor 20. In addition to switch arm 61, the centrifugal mechanism 70 controls a second switch arm 72. When the rotor 71 is at rest or is rotating below a predetermined speed, the switch arms 61 and 72 are in the position shown. However, as the motor comes up to speed, the switch arms are moved down by the centrifugal mechanism 70. As a result, switch arm 61 is disengaged from start winding 56 and moves into engagement with a contact 73, .and switch arm 72 closes to provide connection of the heating element 26 to supply conductor 53.

As the motor comes up to speed then, and switch arm 61 moves into engagement with contact 73, an energizing circuit for main winding 55 is completed independently of push button 62. This is effected, starting at the winding 55, by the circuit which passes through the contact arm 61, contact 73, and conductor 74 and 75, to the contact 63. Thus, when motor 20 comes up to speed and pushbutton 62 is released, the motor continues to run on winding 55 alone, with the parallel start winding 56 disconnected. Also, it will .be seen that the heaters 26 may be energized when the motor has come up to speed as a result of the closing of contact arm 72, but may not be energized when the motor 20 is not running because contact arm 72 is open.

Heaters 26 are connected to a contact 76 of a main control mostat is positioned so as to sense a temperature proportional to that of theclothes. A suitable position for effecting this is that shown in FIGURE 1, wherein the control thermostat 77 is shown as being positioned on the front of the bulkhead .35, directly below the air outlet 45 from the drum. The thermostat 77 is thus effective to sense the temperature of the exhaust air leaving the drum, which temperature is quite close to the actual clothes temperature.

It will be understood that thermostat 77 has a normal low temperature position in which it is in engagement with contact 76 as shown, and also has a high temperature trip position in which it moves into engagement with a contact 78. When the contact arm 79 of thermostat 77 is in its normal position, as shown, an energizing circuit for heater 26 may be completed as follows: starting at conductor 53, the circuit extends through contact arm 72, the heaters v26, contact 76, contact arm 79, conductor 75, contact 63, contact arm 64, and supply conductor 52. In this manner, the heaters 26 may be energized across the full 220 volt source of power.

When the thermostat 77 of contact arm 79 with contact 78 completes an energizing circuit for timer 67 as follows: starting with neutral conductor 54, the circuit passes through switch 57, the timer motor 67, a bimetallic switch element 80, contact 78, contact arm 79, conductor 75, contact 63, and contact arm 64 to supply conductor 52. It will thus be seen that the completion of this energizing circuit for 'the timer motor 67 and the completion of the energizing circuit for heater 26 are alternative in nature, that is, either one or the other is completed depending upon whether the thermostat is in its normal position or is in its tripped position.

Returning now .to the bimetal element 80, it is physically positioned in dryer 1 so as to be responsive to the temperature of ambient air. This may be effected, for instantce, by securing it, as shown, to base 12a adjacent air inlet 51a. Suitable means are provided for causing heating of bimetal 80 in response to completion of the circuit for energizing timer motor 67. Preferably, this is in the form of a heater coil 81 positioned in intimate physical relationship with the bimetal 80, and having its end '82 connected to the bimetal. With this arrangement, When the bimetal is in its closed position the heating coil causes heating of the .bimetal provided the timer circuit is completed. It will, of course, be recognized that there are bimetallic elements which have relative high resistances so that passage of current through them causes them is used, a separate heating coil may not be necessary. The essential point is that there is heating of the bimetal as a direct result of the completion of the timer energizing circuit. When the bimetal 80 is heated to a predetermined temperature it moves to the position shown to open the timer circuit and preclude energization of the timer motor 67.

It will be seen that when the temperature of the ambient air is relatively low, the bimetal 80 must be heated from a relatively low temperature by coil 81 and that therefore a relatively long period of time elapses before the bimetal 80 causes opening of the timer energizing circuit. For higher ambient temperatures, less heating is required and therefore a shorter period of time elapses before the coil 81 causes the bimetal to open the timer circuit. Accordingly, the length of time that the timer runs after each trip of control thermostat 7 7 is determined by the temperature of the ambient air. Thus the necessary corrective action is taken to counteract the increased length of time which the heaters will run when the ambient is low, as compared to the period of time theywill run before tripping when the ambient temperature is high. This is effected by decreasing the total number of heating cycles which occur before the timer tolls the operation. 7

It will be seen from the foregoing that I provide an automatically operative ambient compensation system which, where several trips of the control thermostat are required, compensates for variations in the ambient temperature by modifying the length of time that the timer be of the type which has a relatively slow reset so that there is ample period of time prior to its resetting for the bimetal to control the length of the time the timer operates. This is necessary because as soon as the thersufliciently to reset to the position shown, is re-energized .and the timer is de-energized regardless of the position of bimetal 80.

After the timer has operated for the preselected period of time, the follower 65 enters the dwell in cam 66, as shown, to separate contact arm 64 from contact 63 and cause de-energization of all components of the machine.

While in accordance with the patent statutes I have described what at present is considered to be the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention. In particular, it will readily be apparent that What I claim as new and desire to secure by Letters Patent of the United States is:

1. A clothes dryer comprising:

(a) a chamber for receiving clothes to be dried;

(b) inlet duct means connecting said chamber to the ambient air;

(c) exhaust duct means from said chamber to the ambient air;

(d) air moving means for moving through said inlet duct means said exhaust duct means;

(e) a heater upstream of said chamber for heating air passing into said chamber;

( f) a timer;

(g) a heater circuit for causing operation of said heater;

(h) a timer circuit for causing operation of said timer;

(i) a control thermostat positioned to be responsive to clothes temperatur said control thermostat having a first position at relatively low temperatures and moving to a second position upon sensing a predetermined higher temperature, said control thermostat alternatively enabling completion of said heater circuit and of said timer circuit in said first and second positions respectively;

(j) means controlled by said timer for opening both said circuits after a preselected period of operation of said timer;

(k) and bimetal means positioned in said dryer to sense ambient temperature and arranged in said timer circuit to be heated in response to completion of said timer circuit and to open said timer circuit when said bimetal means reaches a predetermined temperature;

(1) whereby the colder the ambient air the longer said timer circuit is competed each time said control thermostat moves to its second position.

air to said chamber and then out through 2. The apparatus defined in claim 1 wherein means are 7 provided for rotating said chamber in order to tumble clothes therein.

3. The apparatus defined in claim 1 wherein said bimeta-l means includes a bimetal actuated switch in series with said timer, and a resistance heater connected in said timer circuit .to be energized simultaneously with said timer.

4. The apparatus defined in claim 3 wherein said heater is secured at one end to said bimetai switch.

References Cited by the Examiner UNITED STATES PATENTS 2,505,041 4/50 Gorsuch 5 2,875,526 3/59 Engel 2,878,580 3/59 Hughes 2,892,334 6/59 Gray 3,031,768 5/62 Kurowski PERCY L. PATRICK, Primary Examiner. NORMAN YUDKOFF, Examiner. 

1. A CLOTHES DRYER COMPRISING: (Z) A CHAMBER FOR RECEIVING CLOTHES TO BE DRIED; (B) INLET DUCT MEANS CONNECTING SAID CHAMBER TO THE AMBIENT AIR; (C) EXHAUST DUCT MEANS FROM SAID CHAMBER TO THE AMBIENT AIR; (D) AIR MOVING MEANS FOR MOVING AIR TO SAID CHAMBER THROUGH SAID INLET DUCT MEANS AND THEN OUT THROUGH SAID EXHAUST DUCT MEANS; (E) A HEATER UPSTREAM OF SAID CHAMBER FOR HEATING AIR PASSING INTO SAID CHAMBER; (F) A TIMER; (G) A HEATER CIRCUIT FOR CAUSING OPERATION OF SAID HEATER; (H) A TIMER CIRCUIT FOR CAUSING OPERATION OF SAID TIMER; (I) A CONTROL THERMOSTAT POSITIONED TO BE RESPONSIVE TO CLOTHES TEMPERATURE, SAID CONTROL THERMOSTAT HAVING A FIRST POSITION AT RELATIVELY LOW TEMPERATURES AND MOVING TO A SECOND POSITION UPON SENSING A PREDETERMINED HIGHER TEMPERATURE, SAID CONTROL THERMOSTAT ALTERNATIVELY ENABLING COMPLETION OF SAID HEATER CIRCUIT AND OF SAID TIMER CIRCUIT IN SAID FIRST AND SECOND POSITIONS RESPECTIVELY; 